With continued regulatory pressure there is a growing need to identify more environmentally sustainable replacements for refrigerants, heat transfer fluids, foam blowing agents, solvents, and aerosols with lower ozone depleting and global warming potentials. Chlorofluorocarbon (CFC) and hydrochlorofluorocarbons (HCFC), widely used for these applications, are ozone depleting substances and are being phased out in accordance with guidelines of the Montreal Protocol. Hydrofluorocarbons (HFC) are a leading replacement for CFCs and HCFCs in many applications. Though they are deemed “friendly” to the ozone layer they still generally possess high global warming potentials. One new class of compounds that has been identified to replace ozone depleting or high global warming substances are halogenated olefins, such as hydrofluoroolefins (HFO) and hydrochlorofluoroolefins (HCFO). Because of the presence of alkene linkage it is expected that the HFOs and HCFOs will be chemically unstable, relative to HCFCs or CFCs. The inherent chemical instability of these materials in the lower atmosphere results in short atmospheric lifetimes, which provide the low global warming potential and zero or near zero ozone depletion properties desired. However, such inherent instability is believed to also impact the commercial application of such materials, which may degrade during storage, handling and use.
WO 2009/003165 discloses stabilized formulations of HFOs and HCFOs in a variety of applications and compositions. This patent application discloses that stabilizers can be used to inhibit decomposition of HCFO-1233zd during use. WO 2007/002625 discloses the use of various tetrafluoropropenes in a variety of applications including heat transfer systems. The patent application discloses the stability of HFO-1234ze, HFO-1243zf, and HFO-1225ye with selected PAG lubricating oils and compares the results to that of CFC-12 in a mineral oil, using the results to state the refrigerants and compositions of that patent application have better stability than many commonly used refrigerants.
WO08027596, WO08027595, WO08027518, WO08027517, WO08027516, WO08027515, WO08027513, WO08027512, WO08027514 all are directed towards stabilized systems of fluoroolefins. These applications disclose that fluoroolefins can exhibit degradation when exposed to high temperatures or when contacted with other compounds e.g., moisture, oxygen, or other compounds with which they may undergo condensation reactions. It is disclosed that the degradation may occur when fluoroolefins are used as working fluids in heat transfer equipment (refrigeration or air-conditioning equipment, for instance) or when used in some other application. It is disclosed that because of the instability of the fluoroolefins, it may not be practical to incorporate these fluoroolefins into refrigeration or air-conditioning systems. Therefore, to take advantage of the many other attributes of fluoroolefins, means to reduce the degradation via the addition of a stabilizer is needed.
In the present invention, it was discovered that HCFO-1233zd (trans- and/or cis-isomers) and HCFO-1233xf are unexpectedly stable during storage and use without the need for an added stabilizer, being as stable or significantly more stable the many HCFCs and CFCs while being more environmentally sustainable.